Electric motor.



UNITED STATES Patented January 17, 1905.

PATENT CEEICE.

BENJAMIN G. LAMME, OE PITTSBURG, PENNSYLVANIA, ASSIGNCR TO VESTINGIIOUSE ELECTRIC & MANUFACTURING COMPANY, A CCR- PCRATICN CF PENNSYLVANIA.

ELECTRIC MOTOR.

SPECIFICATION forming part of Letters Patent No. 780,047, dated January 17, 1905.

Application filed June 30, 1904. Serial No. 214,819.

To (L7/Z whom, 7175 7mo/7] concern.-

Beit known that I, BENJAMIN Cr. LAMnE, a citizen of the United States, and a resident of Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Electric Motors, of which the following is a specification.

My invention relates to electric motors, and particularly to such motors as employ resistn ance connections between the commutatorbars and the armature-coils for the purpose of preventing' injurious sparking at the commutator.

The object of my invention is to so locate and proportion the resistance-leads which con nect the armature-coils with the commutatorbars that greater mechanical strength may be afforded the structure than could otherwise be obtained.

In the accompanying1 drawings, Figure l is a part-sectional view of an armature and commutator embodying one form of my invention, and Fig. 2 is a similar View of an armature and comi'nutator embodying' another form of my invention.

In the construction of alternating-current electric motors having armatures and commutators similar to those of direct-current motors it has heretofore been proposed to connect the armature-coils with the commutatorsegments by means of leads containing' a suflicient amount of resistance to reduce the current in the armature-coils, which are shortcircuited at any instant by the brushes to such a value that the sparking' between the brushes and the,commutator-bars shall be unobjectionable. Such leads have generally connected the several commutator-bars with the ends of the armature-coils which are nearest to the commutator-cylinder; but it has also been proposed to connect the commutator-segments with the ends of the armature-coils which are remote from the commutator cylinder by means of resistance-leads to be preferably located in the armature-slots. In designing certain sizes of motors, however, it has been found that in order to obtain the required resistance the cross-sectional dimensions of the resistance-leads if arranged as above indicated would be so small as to afford a poor mechanical construction. I have therefore devised another arrangement of leads for such cases which permits of the employment of leads having greater length, and thus for a given resistance provides a greater cross-section of the leads, and therefore greater mechanical strength.

Referring to Fig. l, the end of armaturecoil l which is nearest the commutator-cylin der 2 is connected thereto by means of a rcsistance-lead 3, which is of such cross-section and length as to introduce the desired amount of resistance into the circuit formed whena brush makes contact with two of the commutator-segments. In order to obtain the proper mechanical strength, the resistancelead 3 should have a comparatively large cross-sectional area, its resistance being proportioned by adjusting' its length. The lead is placed in the bottom of the armature-slot, and preferably in the slot that contains one side of the corresponding armature-coil, and it is folded upon itself a suflicient number of times to obtain the proper length for the desired resistance.

In Fig. I the lead is simply doubled upon itself; but it is evident that if a greater resistance is desired the lead may be again doubled upon itself or a construction like that shown in Fig. 2 may be employed, in which the segments of the commutator 2 are severally connected to the ends of the armature-coils l, which are remote from the commutator-cylinder, and the resistance-lead 3 is of three times the length that it would be if it connected the remote end of the armature-coil directly with the corresponding commutator-segment.

It is evident that by means of the construction comprising' my present invention a better mechanical construction is afforded for the resistance-leads than could otherwise be obtained and that almost any desired resistance or any desired cross-section of resistance-lead may be employed.

rIhe invention is of particular advantage in comparatively small sizes of motors, but may be applied to large motors where a great cross- I eommutator, and resistance-leads which conL section of resistance-lead is desired. Not only is the section of the resistance-lead increased, but with this increased section there is an increased radiating-surface, and therefore the loss in the lead is distributed throughout a greater amount of material, the capacity for dissipating` heat being thereby increased. lf

the resistance-leads are folded upon them-f selves an even number of times, the lead bccomes non-inductive.

l claim as my inventionl. An electric motor having` an armature, a commutator and resistance-leads which connect the several commutator-bars to the corresponding armature-coils, said leads being located in the armature-slots and folded on themselves a sufficient number of times to obtain a definite resistance.

2. An electric motor having an armature, a

neet the ends of the armature-coils that are remote from the eommutator to the several commutator-bars, said leads being' located in the armature-slots and being twice folded upon themselves.

3. An electric motor having an armature, a con'nnutator and leads of a definite resistance between the several commutator-bars and the ends of the armature-coils, said leads being` 30 scribed my name this 28th day of J'une, 1904. 35

BENJ. G. LAMME.

l/Vitnesses:

E. M. S'riiwAR'r, BIRNEY HINEs. 

